TLR3 signaling modulates immunomodulatory property of human periodontal ligament stem cells.

Abstract

Toll like receptor 3 (TLR3) is a member of TLR family functions to recognizes double-stranded RNA (dsRNA) produced by positive-strand RNA viruses and DNA virusesand generate signaling that stimulate body immune system against virus infection. However, recent evidence suggests that TLR3 signaling may also play a role in initiating the immunosuppressive property of the cells. Study on skin regeneration has shown the anti-inflammatory responses of keratinocytes required for wound healing andthe increasing number of hair follicle formation after TLR3 signaling was activated by fragment of RNA released from damaged cells. Moreover, activation of TLR3 signaling have shown to elicit a higher success rate and lower side-effect for a grafted surgery in animal models. Taken together, TLR3 signaling may play an important role in immunomodulatory property of the cells. The aim of this study is to investigate the involvement of TLR3 signaling on immunomodulatory properties in periodontal ligament stem cells (PDLSCs). PDLSCs expressed TLR3, however, detailed mechanism in which TLR3 signaling modulate immunomodulatory property of PDLSCs has not yet been identified. PDLSCs were established from is periodontal tissue and expressed several multipotent stem cells markers. These cells could also differentiate under appropriate culture conditions. After activation with poly(I:C), a potent activator of TLR3, the expression of interferon-gamma, IDO (indolamine 2,3 dioxygenase) and HLA-G (human leukocyte antigen G), three major molecules that participate in the immunomodulatory function. Addition of bafilomycin A, a chemical inhibitor that prevent the cytoplasmic acidity, could inhibit this inductive property, indicating that activated TLR3 were located in cytoplasmic endosome. RNA silencing approaches could also abolish the inductive effect of poly(I:C) confirming the role of TLR3. Furthermore, the co-culture between poly(I:C)-treated PDLSCs and PBMCs was performed. The results showed the inhibitory effect of PBMCs and the upregulation of FOXO3, a marker of T-regulatory cells support the immunomodulatory role of PDLSCs after activated with poly(I:C). The knowledge from this study will provide more understanding on TLR3-induced immunosuppressive property on PDLSCs that could lead to the clinical application for stem cells therapy in the future.